Process for RIE etching silicon dioxide

Abstract

An improved RIE process is disclosed for etching one or more openings in a layer of an oxide of silicon on a semiconductor wafer characterized by a contact angle of at least 80°, with respect to the plane of the oxide layer, and highly selective to silicon which comprises flowing an inert gas and CHF 3 into an RIE chamber while maintaining respective gas flows within a range of from about 15 to about 185 sccm of inert gas and from about 15 to about 60 sccm of CHF 3 , with a total gas flow not exceeding about 200 sccm, and a ratio of inert gas to CHF 3 ranging from about 1:1 to about 10:1. A plasma is maintained in the RIE chamber during the gas flow at a power level within a range of from about 400 to about 1000 watts. In a preferred embodiment, CF 4 gas is also flowed into the RIE chamber within a range of from about 1 to about 10 sccm to control the selectivity of the etch to silicon, and the wafer is immersed in a magnetic field of 1 to 120 gauss during the etching process.

Having thus described the invention, what is claimed is: 
     
       1. An improved RIE process for etching an oxide of silicon characterized by a nearly vertical contact angle and highly selective to silicon which comprises flowing from about 15 to about 185 sccm of an inert gas and from about 15 to about 60 sccm of CHF 3  into an RIE chamber while maintaining a plasma therein at a power level within a range of from about 400 to about 1000 watts. 
     
     
       2. The process of claim 1 wherein said step of flowing said inert gas and said CHF 3  gas into said RIE chamber further comprises flowing said gases into said chamber while maintaining a ratio between said gases within a range of from about 1:1 to about 10:1 of inert gas:CHF 3 . 
     
     
       3. The process of claim 2 wherein the total flow of gases into said RIE chamber does not exceed about 200 sccm. 
     
     
       4. The process of claim 3 wherein said inert gas is selected from the class consisting of helium and argon. 
     
     
       5. The process of claim 4 wherein said inert gas comprises argon. 
     
     
       6. The process of claim 3 wherein said RIE chamber is maintained at a pressure during said etching within a range of from about 10 to about 120 milliTorr. 
     
     
       7. The process of claim 3 wherein the temperature of said wafer in said RIE chamber is maintained within a range of from about 15° C. to about 25° C. during said etching step. 
     
     
       8. The process of claim 3 wherein said wafer is immersed in a magnetic field during said etching step, said magnetic field having a field strength of up to 120 gauss and a magnetic moment in a direction parallel to the plane of said wafer. 
     
     
       9. The process of claim 3 wherein said step of flowing said gases into said chamber further comprises flowing CF 4  into said chamber in an amount within a range of from about 1 to about 10 sccm. 
     
     
       10. The process of claim 9 wherein said amount of said CF 4  gas into said chamber is within a range of from about 2 to about 6 sccm. 
     
     
       11. An improved RIE process for etching one or more openings in a layer of an oxide of silicon characterized by a contact angle of at least 80°, with respect to the plane of said oxide layer, and highly selective to silicon which comprises: (a) flowing an inert gas, CHF 3 , and CF 4  into an RIE chamber while maintaining said respective gas flows within a range of from about 30 to about 140 sccm of said inert gas, from about 15 to about 60 sccm of said CHF3 and from about 1 to about 10 sccm of said CF 4 , with the total amount of said gases not exceeding about 200 sccm; and   (b) maintaining a plasma in said RIE chamber during said gas flow at a power level within a range of from about 400 to about 1000 watts.   
     
     
       12. The process of claim 11 wherein said step of flowing said gases into said RIE chamber further comprises flowing said gases into said chamber while maintaining a ratio between said inert gas and said CHF 3  within a range of from about 2:1 to about 5:1. 
     
     
       13. The process of claim 12 wherein said inert gas is selected from the class consisting of helium and argon. 
     
     
       14. The process of claim 12 wherein said wafer is immersed in a magnetic field during said etching step, said magnetic field having a field strength of up to 120 gauss and a magnetic moment in a direction parallel to the plane of said wafer. 
     
     
       15. The process of claim 12 wherein said amount of said CF 4  gas into said chamber is within a range of from about 2 to about 6 sccm. 
     
     
       16. An improved RIE process for etching one or more openings in a layer of an oxide of silicon characterized by a contact angle of at least 80°, with respect to the plane of said oxide layer, and highly selective to silicon which comprises: (a) flowing argon, CHF 3 , and CF 4  into an RIE chamber while maintaining said respective gas flows within a range of from about 30 to about 140 sccm of said argon, from about 15 to about 60 sccm of said CHF 3  and from about 2 to about 6 sccm of said CF 4 , with the total amount of said gases not exceeding about 200 sccm, and while maintaining a ratio between said argon and said CHF 3  gases within a range of from about 2:1 to about 5:1;   (b) maintaining a plasma in said RIE chamber during said gas flow at a power level within a range of from about 400 to about 1000 watts; and   (c) continuing to flow said gases into said chamber and maintaining said plasma in said chamber to etch said oxide of silicon until an underlying layer of silicon is reached.   
     
     
       17. The process of claim 16 wherein said wafer is immersed in a magnetic field during said etching step, said magnetic field having a field strength of up to 120 gauss and a magnetic moment in a direction parallel to the plane of said wafer. 
     
     
       18. The process of claim 16 wherein said RIE chamber is maintain at a pressure during said etching within a range of from about 10 to about 120 millitorr. 
     
     
       19. The process of claim 16 wherein the temperature of said wafer in said RIE chamber is maintained within a range of from about 15° C. to about 25° C. during said etching step. 
     
     
       20. An improved RIE process for etching one or more openings in a layer of an oxide of silicon characterized by a contact angle of at least 80°, with respect to the plane of said oxide layer, and highly selective to silicon which comprises: (a) flowing argon, CHF 3 , and CF 4  into an RIE chamber while maintaining said respective gas flows within a range of from about 30 to about 140 sccm of said argon, from about 15 to about 60 sccm of said CHF 3  and from about 2 to about 6 sccm of said CF 4 , with the total amount of said gases not exceeding about 200 sccm, and while maintaining a ratio between said argon and said CHF 3  gases within a range of from about 2:1 to about 5:1;   (b) maintaining a plasma in said RIE chamber during said gas flow at a power level within a range of from about 400 to about 1000 watts;   (c) immersing said wafer in a magnetic field having a field strength of up to 120 gauss and a magnetic moment in a direction parallel to the plane of said wafer; and   (d) continuing to flow said gases into said chamber and maintaining said plasma in said chamber to etch said oxide of silicon while immersed in said magnetic field until an underlying layer of silicon is reached.